Wt  4.0.2
Public Member Functions | List of all members
Wt::WAbstractItemDelegate Class Referenceabstract

Abstract delegate class for rendering an item in an item view. More...

#include <Wt/WAbstractItemDelegate.h>

Inheritance diagram for Wt::WAbstractItemDelegate:
Inheritance graph
[legend]

Public Member Functions

 WAbstractItemDelegate ()
 Constructor.
 
virtual ~WAbstractItemDelegate ()
 Destructor.
 
virtual std::unique_ptr< WWidgetupdate (WWidget *widget, const WModelIndex &index, WFlags< ViewItemRenderFlag > flags)=0
 Creates or updates a widget that renders an item. More...
 
virtual void updateModelIndex (WWidget *widget, const WModelIndex &index)
 Updates the model index of a widget. More...
 
virtual cpp17::any editState (WWidget *widget, const WModelIndex &index) const
 Returns the current edit state. More...
 
virtual void setEditState (WWidget *widget, const WModelIndex &index, const cpp17::any &value) const
 Sets the editor data from the editor state. More...
 
virtual ValidationState validate (const WModelIndex &index, const cpp17::any &editState) const
 Returns whether the edited value is valid. More...
 
virtual void setModelData (const cpp17::any &editState, WAbstractItemModel *model, const WModelIndex &index) const
 Saves the edited data to the model. More...
 
Signal< WWidget *, bool > & closeEditor ()
 Signal which indicates that an editor needs to be closed. More...
 
const Signal< WWidget *, bool > & closeEditor () const
 Signal which indicates that an editor needs to be closed. More...
 
- Public Member Functions inherited from Wt::WObject
void addChild (std::unique_ptr< WObject > child)
 Add a child WObject whose lifetime is determined by this WObject.
 
template<typename Child >
Child * addChild (std::unique_ptr< Child > child)
 Add a child WObject, returning a raw pointer. More...
 
std::unique_ptr< WObjectremoveChild (WObject *child)
 Remove a child WObject, so its lifetime is no longer determined by this WObject.
 
virtual const std::string id () const
 Returns the (unique) identifier for this object. More...
 
virtual void setObjectName (const std::string &name)
 Sets an object name. More...
 
virtual std::string objectName () const
 Returns the object name. More...
 
void resetLearnedSlots ()
 Resets learned stateless slot implementations. More...
 
template<class T >
void resetLearnedSlot (void(T::*method)())
 Resets a learned stateless slot implementation. More...
 
template<class T >
WStatelessSlot * implementStateless (void(T::*method)())
 Declares a slot to be stateless and learn client-side behaviour on first invocation. More...
 
template<class T >
WStatelessSlot * implementStateless (void(T::*method)(), void(T::*undoMethod)())
 Declares a slot to be stateless and learn client-side behaviour in advance. More...
 
void isNotStateless ()
 Marks the current function as not stateless. More...
 
template<class T >
WStatelessSlot * implementJavaScript (void(T::*method)(), const std::string &jsCode)
 Provides a JavaScript implementation for a method. More...
 
- Public Member Functions inherited from Wt::Core::observable
 observable () noexcept
 Default constructor.
 
virtual ~observable ()
 Destructor. More...
 

Additional Inherited Members

- Public Types inherited from Wt::WObject
typedef void(WObject::* Method) ()
 Typedef for a WObject method without arguments.
 
- Protected Member Functions inherited from Wt::WObject
virtual WStatelessSlot * getStateless (Method method)
 On-demand stateless slot implementation. More...
 

Detailed Description

Abstract delegate class for rendering an item in an item view.

Rendering of an item in a WAbstractItemView is delegated to an implementation of this delegate class. The default implementation used by Wt's item views is WItemDelegate. To provide specialized rendering support, you can reimplement this class (or specialize WItemDelegate).

As a delegate is used for rendering multiple items, the class should not keep state about one specific item.

A delegate may provide editing support by instantiating an editor when update() is called with the Wt::ViewItemRenderFlag::Editing flag. In that case, you will also need to implement editState() and setEditState() to support virtual scrolling and setModelData() to save the edited value to the model. For an example, see the WItemDelegate.

See also
WAbstractItemView::setItemDelegateForColumn()

Member Function Documentation

Signal<WWidget *, bool>& Wt::WAbstractItemDelegate::closeEditor ( )

Signal which indicates that an editor needs to be closed.

The delegate should emit this signal when it decides for itself that it should be closed (e.g. because the user confirmed the edited value or cancelled the editing). The View will then rerender the item if needed.

The second boolean argument passed to the signal is a flag which indicates whether the editor feels that the value should be saved or cancelled.

See also
WAbstractItemView::closeEditor()
const Signal<WWidget *, bool>& Wt::WAbstractItemDelegate::closeEditor ( ) const

Signal which indicates that an editor needs to be closed.

See also
closeEditor()
cpp17::any Wt::WAbstractItemDelegate::editState ( WWidget widget,
const WModelIndex index 
) const
virtual

Returns the current edit state.

Because a View may support virtual scrolling in combination with editing, it may happen that the view decides to delete the editor widget while the user is editing. To allow to reconstruct the editor in its original state, the View will therefore ask for the editor to serialize its state in a boost::any.

When the view decides to close an editor and save its value back to the model, he will first call editState() and then setModelData().

The default implementation assumes a read-only delegate, and returns a boost::any().

See also
setEditState(), setModelData()

Reimplemented in Wt::WItemDelegate.

void Wt::WAbstractItemDelegate::setEditState ( WWidget widget,
const WModelIndex index,
const cpp17::any &  value 
) const
virtual

Sets the editor data from the editor state.

When the View scrolls back into view an item that was being edited, he will use setEditState() to allow the editor to restore its current editor state.

The default implementation assumes a read-only delegate and does nothing.

See also
editState()

Reimplemented in Wt::WItemDelegate.

void Wt::WAbstractItemDelegate::setModelData ( const cpp17::any &  editState,
WAbstractItemModel model,
const WModelIndex index 
) const
virtual

Saves the edited data to the model.

The View will use this method to save the edited value to the model. The editState is first fetched from the editor using editState().

The default implementation assumes a read-only delegate does nothing.

Reimplemented in Wt::WItemDelegate.

virtual std::unique_ptr<WWidget> Wt::WAbstractItemDelegate::update ( WWidget widget,
const WModelIndex index,
WFlags< ViewItemRenderFlag flags 
)
pure virtual

Creates or updates a widget that renders an item.

The item is specified by its model index, which also indicates the model. If an existing widget already renders the item, but needs to be updated, it is passed as the widget parameter.

When widget is nullptr, a new widget needs to be created and returned.

If you want to replace the widget with a new one, return the new widget. The old widget will be removed. Return nullptr if you do not want to replace the widget.

You can remove the widget from its parent for reuse with WWidget::removeFromParent().

The returned widget should be a widget that responds properly to be given a height, width and style class. In practice, that means it cannot have a border or margin, and thus cannot be a WFormWidget since those widgets typically have built-in borders and margins. If you want to return a form widget (for editing the item), you should wrap it in a container widget.

The flags parameter indicates options for rendering the item.

Implemented in Wt::WItemDelegate.

void Wt::WAbstractItemDelegate::updateModelIndex ( WWidget widget,
const WModelIndex index 
)
virtual

Updates the model index of a widget.

This method is invoked by the view when due to row/column insertions or removals, the index has shifted.

You should reimplement this method only if you are storing the model index in the widget, to update the stored model index.

The default implementation does nothing.

Reimplemented in Wt::WItemDelegate.

ValidationState Wt::WAbstractItemDelegate::validate ( const WModelIndex index,
const cpp17::any &  editState 
) const
virtual

Returns whether the edited value is valid.

The default implementation does nothing and returns Valid.

See also
WValidator::validate()

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